Numerical investigation of the unsteady multiphase flow around a supercavitating vehicle with scarfed gas jets

To address tail slamming during high-speed water entry, this study proposes an active stabilization method using scarfed gas jets at the tail, enhancing vehicle attitude control through the reactive forces of the jets and the interference it generates. Numerical simulations of the supersonic gas jet flows within the natural supercavity are conducted using the RANS turbulence model coupled with the mixture multiphase flow model. The evolution of the gas-vapor-liquid multiphase flow field and nozzle thrust characteristics under different cavitation numbers and angles of attack (AOAs) are analyzed, and the potential effects and dynamic mechanisms of the scarfed jets on vehicle motion stability are investigated. The results show that jet control induces bidirectional axial expansion of the gas bubbles, thereby increasing the clearance between the vehicle tail and the cavity boundary. The asymmetric inflow modifies the operating state of the vertically opposed nozzles, leading to an underexpanded leeward jet and an overexpanded windward jet. The resulting asymmetric redistribution of wall pressure is identified as the primary source of pitching moment variation, surpassing the contribution of direct jet thrust. The scarfed gas jet promotes a nose-down restoring tendency at α = 2° and suppresses a nose-up overturning tendency at α = 4°, effectively enhancing the attitude stability of the vehicle. As the cavitation number increases, the reduction in supercavity volume, along with the wetted exhaust section and high-pressure gas accumulation on the leeward side of the tail, diminishes the control effectiveness.